1. Field of Invention
The present invention relates generally to mechanisms for selecting gears in transmissions. More particularly, it relates to an apparatus for selecting a gear and holding the gear selection in automotive manual type transmissions, especially for automobile racing applications.
2. Background Art
Conventional automotive gear selection mechanisims, called Shifters permit a driver via a shift lever to selectively engage gears in the transmission. The other gears which are not engaged are left in a neutral or disengaged position. These conventional shifters generally position gears in the transmission through linkages between arms on the shifter positioned by the shift lever and selection arms attached to shifting shafts in the body of the transmission. These shafts are usually held in place within the transmission by spring loaded detents. These detents are the sole means of holding gears in position. In addition, certain types of conventional shifters have features which prevent unintended engagement of the reverse gear set and/or selection of the neutral position by the driver. These features generally prevent the shift lever from being moved to the reverse or neutral position without releasing a stop. There is generally nothing incorporated in conventional shifters to prevent movement of the shift, lever, arms, linkages or shafts.
Conventional shifters with or without these features have the following drawbacks. In certain racing applications, especially in dirt track racing, irregular track surfaces, frequent contact between competing cars and rapid engine speed variations constantly impose stresses on the race car. These stresses often overcome the relatively weak restraints provided by the spring loaded detents and cause transmissions with conventional shifters to jump out of gear or cause two gear sets in the transmission to engage simultaneously. When a transmission jumps out of gear, loss of control often ensues because steering is accomplished by a combination of steering with the front wheels and slippage of the spinning rear wheels. This slippage of the rear wheels is controlled by the driver's use of the throttle to control engine speed which is transferred through the transmission to the rear wheels. When the transmission jumps out of gear into neutral, this steering function of the rear wheels is lost resulting in loss of control over the car. Often this results in a accident with serious damage to one or more cars on the track and in some cases injury to the drivers. In addition, since the engines are often operating near their maximum RPM limit when the transmission suddenly jumps out of gear the engine almost instantly exceeds its maximum RPM limit, and extensive mechanical damage to the engine can and often does result.
The second drawback mentioned above, the accidental engagement of more than one gear at a time in the transmission is also encountered with conventional shifter mechanisms. Here again, the imposed stresses overcome the restraints of the detents, the unrestrained shiftarm of a conventional shifting mechanism which locates a controlled gear set in a neutral position is jarred into an engaged position. When this occurs the transmission is almost invariably seriously damaged and the driver experiences a loss of control similar to that described when the transmission jumps out of gear.
Another problem that is associated with conventional shifter mechanisms is hanging up a gear; that is the occasional inability to disengage a gear selection. This occurs when either the shifter suffers from excessive wear or slippage occurs between the shaft that enters the transmission and the shift arm attached to it. When hangups occur, the conventional shifter with a single shift lever, can not function to disengage the gear set already engaged while simultaneously engaging another gear set which is activated by a separate shift arm. This occurs because the wear or slippage prevents the adjacent shift arms in the shifter from aligning properly so that the shift lever can move from one arm to engage the second arm to effect disengagement of one gear set and engagement of the other.